Commit 5df66d30 authored Aug 21, 2018 by Oscar Salvador Committed by Linus Torvalds Aug 22, 2018

mm: fix comment for NODEMASK_ALLOC

Currently, NODEMASK_ALLOC allocates a nodemask_t with kmalloc when
NODES_SHIFT is higher than 8, otherwise it declares it within the stack.

The comment says that the reasoning behind this, is that nodemask_t will
be 256 bytes when NODES_SHIFT is higher than 8, but this is not true. For
example, NODES_SHIFT = 9 will give us a 64 bytes nodemask_t. Let us fix
up the comment for that.

Another thing is that it might make sense to let values lower than
128bytes be allocated in the stack. Although this all depends on the
depth of the stack (and this changes from function to function), I think
that 64 bytes is something we can easily afford. So we could even bump
the limit by 1 (from > 8 to > 9).

Link: http://lkml.kernel.org/r/20180820085516.9687-1-osalvador@techadventures.net

Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent c8bd134a

include/linux/nodemask.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -518,7 +518,7 @@ static inline int node_random(const nodemask_t *mask)
		* NODEMASK_ALLOC(type, name) allocates an object with a specified type and
		* name.
		*/
		#if NODES_SHIFT > 8 /* nodemask_t > 256 bytes */
		#if NODES_SHIFT > 8 /* nodemask_t > 32 bytes */
		#define NODEMASK_ALLOC(type, name, gfp_flags) \
		type name = kmalloc(sizeof(name), gfp_flags)
		#define NODEMASK_FREE(m) kfree(m)

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